Immunohistochemical identification of
keratin proteins (TK, KL1 and PKK1),
vimentin,
myosin,
S-100 protein (using polyclonal antiserum) and S-100 alpha and beta subunits,
glial fibrillary acidic protein (GFAP),
neuron-specific enolase (NSE),
lactoferrin, and
lysozyme was made in
myoepitheliomas, myoepithelial
adenomas, and clear cell
adenomas of salivary gland origin.
Myoepithelioma cells were divided into two types: plasmacytoid cells, which showed great heterogeneity in terms of
keratins and S-100 alpha and beta
proteins and a lack of GFAP, NSE,
lactoferrin, and
lysozyme in most the cells, and fibrous and dendritic
tumor cells, which displayed variable staining for
keratin and S-100 alpha and beta
proteins. Myoepithelial
adenomas were composed of small-, intermediate-, and large-sized spindle cells that showed irregular positive reactions for
keratins and S-100 alpha and beta. Immunohistochemical deposition of
S-100 protein was restricted strongly to the dendritic cells present in hyalinous and myxomatous areas. Clear cell
adenomas revealed uniformly slight staining of
keratins and S-100
proteins, and negative staining or rarely positivity for GFAP, NSE,
lactoferrin, and
lysozyme. When the immunohistochemical deposition of these
proteins was compared between normal glands and
myoepithelial tumors, heterogeneity of expression of
keratins, S-100
proteins, GFAP, and NSE was notable in the
tumors. Progenitor cells of several kinds of
myoepithelioma were suggested to be intercalated reserve cells, which are thought to be the same cell that gives rise to
pleomorphic adenoma of salivary glands.